Glioblastoma multiforme (GBM), accounting for 60 to 70% of malignant gliomas, is the most aggressive form of gliomas and the most common primary brain tumor in adults (Louis D N, et al. (2007) The 2007 WHO classification of tumours of the central nervous system. Acta Neuropathol 114(2):97-109). Despite many treatments, including surgery, and chemo- or radiotherapy available for GBM, the prognosis and survival rate for GBM patients are still poor, with the median survival rate of 14-15 months (Van Meir E G, et al. (2010) Exciting new advances in neuro-oncology: the avenue to a cure for malignant glioma. CA Cancer J Clin 60 (Meyer M A (2008) Malignant gliomas in adults. N Engl J Med 359(17):1850; author reply 1850):166-193). GBM is notoriously resistant to most anti-cancer drugs and extremely infiltrative, which hampers complete surgical resection, and therefore most patients develop tumor recurrence or progression even after multiple therapies. Because of the high mortality, new therapeutic approaches, such as immunotherapy and gene therapy, have been proposed for the treatment of GBM (Meyer M A (2008) Malignant gliomas in adults. N Engl J Med 359(17):1850; author reply 1850).
Altered glycosylation is a feature of cancer cells, and several glycan structures are well-known tumor markers (Meezan E, Wu H C, Black P H, & Robbins P W (1969) Comparative studies on the carbohydrate-containing membrane components of normal and virus-transformed mouse fibroblasts. II. Separation of glycoproteins and glycopeptides by sephadex chromatography. Biochemistry 8(6):2518-2524; Hakomori S (2002) Glycosylation defining cancer malignancy: new wine in an old bottle. Proc Natl Acad Sci USA 99(16):10231-10233). These aberrant changes include the overall increase in the branching of N-linked glycans (Lau K S & Dennis J W (2008) N-Glycans in cancer progression. Glycobiology 18(10):750-760) and sialic acid content (van Beek W P, Smets L A, & Emmelot P (1973) Increased sialic acid density in surface glycoprotein of transformed and malignant cells—a general phenomenon? Cancer Res 33(11):2913-2922), and the overexpression of certain glycan epitopes, such as sialyl Lewis x (sLex), sialyl Tn (sTn), Lewis y (Ley), Globo H, and polysialic acid (Sell S (1990) Cancer-associated carbohydrates identified by monoclonal antibodies. Hum Pathol 21(10):1003-1019; Hakomori S & Zhang Y (1997) Glycosphingolipid antigens and cancer therapy. Chem Biol 4(2):97-104; Taylor-Papadimitriou J & Epenetos A A (1994) Exploiting altered glycosylation patterns in cancer: progress and challenges in diagnosis and therapy. Trends Biotechnol 12(6):227-233). Many tumors also exhibit increased expression of certain glycolipids, especially the gangliosides, glycosphingolipids (GSLs) with sialic acid(s) attached to the glycan chain. Gangliosides are normally observed in neural systems, and are found to be elevated in tumors, particularly the complex gangliosides associated with malignancy (Birkle S, Zeng G, Gao L, Yu R K, & Aubry J (2003) Role of tumor-associated gangliosides in cancer progression. Biochimie 85(3-4):455-463).
It has been reported that human glioma show expression of ganglosides (Fredman P, et al. (1986) Potential ganglioside antigens associated with human gliomas. Neurol Res 8(2):123-126; Yates A J, Becker L E, & Sachs L A (1979) Brain tumors in childhood. Childs Brain 5(1):31-39; Traylor T D & Hogan E L (1980) Gangliosides of human cerebral astrocytomas. J Neurochem 34(1):126-131; Berra B, Gaini S M, & Riboni L (1985) Correlation between ganglioside distribution and histological grading of human astrocytomas. Int J Cancer 36(3):363-366; Fredman P, von Holst H, Collins V P, Granholm L, & Svennerholm L (1988) Sialyllactotetraosylceramide, a ganglioside marker for human malignant gliomas. J Neurochem 50(3):912-919; Mansson J E, et al. (1986) Characterization of new gangliosides of the lactotetraose series in murine xenografts of a human glioma cell line. FEBS Lett 201(1):109-113; Fredman P, von Holst H, Collins V P, Dellheden B, & Svennerholm L (1993) Expression of gangliosides GD3 and 3′-isoLM1 in autopsy brains from patients with malignant tumors. J Neurochem 60(1):99-105). Since some of glioma-associated gangliosides are rarely expressed or even absent in normal tissues (Svennerholm L, et al. (1989) Human brain gangliosides: developmental changes from early fetal stage to advanced age. Biochim Biophys Acta 1005(2):109-117), they are suitable for targeted therapy (Kato Y, et al. (2010) GMab-1, a high-affinity anti-3′-isoLM1/3′,6′-isoLD1 IgG monoclonal antibody, raised in lacto-series ganglioside-defective knockout mice. Biochem Biophys Res Commun 391(1):750-755). Hence, discovering novel glioma-associated GSLs would provide new targets for development of new therapies against gliomas.
The GSLs of globo-series feature a Galα1-4Gal linkage to lactosylceramides, and this linkage is catalyzed by lactosylceramide 4-alpha-galactosyltransferase (A4GALT). While globotriosylceramide (Gb3Cer) and globoside (Gb4Cer) constitute the basis of P-blood group system (Schenkel-Brunner H (1995) P System. Human Blood Groups, (Springer Vienna), pp 211-234), galactosyl globoside (Gb5Cer) and sialyl galactosyl globoside (sialyl Gb5Cer, SGG, MSGG), also known as stage-specific embryonic antigen-3 (SSEA-3) and SSEA-4 (Kannagi R, et al. (1983) Stage-specific embryonic antigens (SSEA-3 and -4) are epitopes of a unique globo-series ganglioside isolated from human teratocarcinoma cells. EMBO J 2(12):2355-2361), respectively, are widely used as cell-surface markers to define human embryonic stem cells. Globo-series GSLs have also been observed in tumors: Globo H (fucosyl Gb5Cer) is overexpressed in many epithelial cancers, such as ovarian, gastric, prostate, lung, breast, and pancreatic cancers (Zhang S, et al. (1997) Selection of tumor antigens as targets for immune attack using immunohistochemistry: I. Focus on gangliosides. Int J Cancer 73(1):42-49); SSEA-3, SSEA-4 and Globo H are expressed not only on breast cancer cells, but also on breast cancer stem cells (Chang W W, et al. (2008) Expression of Globo H and SSEA3 in breast cancer stem cells and the involvement of fucosyl transferases 1 and 2 in Globo H synthesis. Proc Natl Acad Sci USA 105(33):11667-11672; Huang Y L, et al. (2013) Carbohydrate-based vaccines with a glycolipid adjuvant for breast cancer. Proc Natl Acad Sci USA 110(7):2517-2522). Moreover, in renal cell carcinoma, high-level expressions of SSEA-4 and disialosyl galactosyl globoside (disialosyl Gb5Cer, DSGG) are observed (Saito S, et al. (1997) Expression of globo-series gangliosides in human renal cell carcinoma. Jpn J Cancer Res 88(7):652-659), but it is still not known whether globo-series GSLs are expressed on GBM.
It is of great interest to identify glycan markers associated with and/or predictive of cancers, and develop antibodies against the markers for use in diagnosing and treating a broad spectrum of cancers.